All images and videos on Pixabay are released free of copyrights under Creative Commons CCO. You may download, modify, distribute, and use them royalty free for anything you like, even in commercial applications. Attribution is not required.
Pixabay does have some premium images in their results but these are clearly marked with the shutterstock watermark so you can’t accidentally download and use an image that is not available for use under the Creative Commons license.
As with the other image resources we have listed on this website (www.tipsforyourwebsite.com) you don’t even have to sign up for an account.